Device for control of an electric fuel pump

ABSTRACT

The invention relates to a device for control of an electric fuel pump ( 1, 2 ) on a motor vehicle, whereby, on a fault in an electronic controller ( 3 ), the fuel pump ( 1, 2 ) is connected to the voltage supply of the vehicle. The fuel pump ( 1, 2 ) then pumps at full capacity. Said device offers a high security against a break in the supply of fuel.

[0001] The invention relates to a device for actuating an electric fuelpump for a motor vehicle having an electronic controller for regulatingthe power of the fuel pump, said controller being arranged between apower supply and the fuel pump, and having a pressure sensor formonitoring a pressure which is generated by the fuel pump.

[0002] Such devices are used in motor vehicles today and are known frompractice. As a result, the fuel pump can be regulated as a function ofthe demand of the internal combustion engine of the motor vehicle. Theinternal combustion engine therefore receives from the fuel pump onlythe quantity of fuel which it requires.

[0003] Unnecessary agitation and heating of fuel in the fuel containeris avoided with the known device. As a result, the fuel container has alow level of permeation of fuel.

[0004] A disadvantage with the known device is that when the electroniccontroller fails the fuel pump is no longer actuated, and the fuel isthus not fed.

[0005] The invention is based on the problem of developing a device ofthe known type in such a way that when the electronic controller failsthe fuel pump can continue to operate at least temporarily.

[0006] This problem is solved according to the invention in that theelectronic controller is connected to a monitoring device, and in thatmeans for connecting the fuel pump to the power supply when theelectronic controller has a fault are provided.

[0007] As a result of this configuration, it is ensured that the fuelpump is supplied with power even when the electronic controller has afault. The fuel pump therefore continues to operate despite the fault.As a result, when there is a fault in the electronic controller, afailure to supply the internal combustion engine with fuel is reliablyavoided. The monitoring device may be, for example, what is referred toas a watch dog.

[0008] According to one advantageous development of the invention, whenthe pressure sensor fails it is ensured that the internal combustionengine is supplied with fuel if the electronic controller or themonitoring device has means for the unregulated connection of the fuelpump to the power supply when the pressure sensor has a fault.

[0009] The connection of the fuel pump to the power supply could have,for example, a standby controller. However, the device according to theinvention is of particularly simple design if the connection to thepower supply is unregulated.

[0010] The device according to the invention is of particularly simplestructural design if the fuel pump has a switch, if the switch can beactuated by the monitoring device and is designed to connect the fuelpump to the electronic controller in one position, and to the powersupply in the other position.

[0011] According to another advantageous development of the invention,the switching over from the regulated control of the fuel pump into theunregulated control requires particularly low structural expenditure ifthe switch has a relay.

[0012] In particularly high-power internal combustion engines, two fuelpumps are frequently used. According to another advantageous developmentof the invention, the regulation of the power of a plurality of fuelpumps requires particularly little expenditure if a single electroniccontroller is designed to actuate a plurality of fuel pumps.

[0013] The unregulated connection of the fuel pump could have, forexample, a fixed resistance, and permit the fuel pump to operate in thepartial load range. The device according to the invention permitspermanent operation of the fuel pump under full load if the fuel pump isconnected to a mechanical pressure regulator. By means of thisconfiguration, the operation of the fuel pump with the unregulatedconnection to the power supply is the same as that of the known fuelpump without an electronic controller.

[0014] When there are a plurality of fuel pumps, a single switch couldform the connection to the power supply or to the electronic controller.However, the device according to the invention has a particularly highlevel of failsafeness if each of the fuel pumps has its own switch.

[0015] According to another advantageous development of the invention,checking the operational capability of the electronic controllerrequires particularly low expenditure if the monitoring device and thecontrol unit of the internal combustion engine have a common connectionfor a diagnostic device. At the same time, the electronic controller,the pressure regulator and the monitoring device can easily be testedusing the control unit of the internal combustion engine which has to bechecked regularly anyway.

[0016] The invention permits numerous embodiments. In order to clarifyits basic principle further, one of them is illustrated in the drawingand will be described below.

[0017] The drawing shows, in a single FIGURE, a schematic view of adevice according to the invention for regulating the power of two fuelpumps 1, 2. The device has an electronic controller 3 and a monitoringdevice 4. The electronic controller 3 is connected to a control unit 5of an internal combustion engine of the motor vehicle and to a pressuresensor 7 which is arranged in an injection rail 6. As a result, theelectronic controller 3 can regulate the power of the fuel pumps 1, 2 asa function of the signals of the control unit 5 and the pressureprevailing in the injection rail 6.

[0018] A signal which is generated by the electronic controller 3 ischecked by the monitoring device 4. The monitoring device 4 is connectedto a relay 8. The relay 8 actuates two switches 9, 10 which form theconnection of the fuel pumps 1, 2 either to the power supplycharacterized in the drawing by V+ and ground, or to the electroniccontroller 3. The electronic controller 3 has a regulator 11, apulse-width modulation means 12 and two control units 13, 14. Thecontrol units 13, 14 are each assigned to a fuel pump 1, 2.

[0019] The control unit 5 of the internal combustion engine and themonitoring device 4 are connected to a common diagnostic connection 15.In addition, the control signals of the monitoring device 4 aretransmitted to the relay 8 via the line 16 which leads to the diagnosticconnection 15.

[0020] A failure of the electronic controller 3 is sensed by themonitoring device 4. The monitoring device 4 actuates the relay 8 whenthe electronic controller 3 fails, and the said relay 8 then switchesover the connection of the fuel pumps 1, 2 from the electroniccontroller 3 to the power supply. As a result, the fuel pumps 1, 2 areoperated with full power in an unregulated fashion. The pressuregenerated by the fuel pumps 1, 2 is limited to, for example, 6 bar by amechanical pressure regulator 17. Excess fuel is fed back into the fuelcontainer via a cut-off line 18.

[0021] If the fuel pumps 1, 2 are regulated by means of the electroniccontroller 3, the pressure generated in the injection rail 6 is alwaysheld below 6 bar so that the mechanical pressure regulator 17continuously closes the cut-off line 18.

1. A device for actuating an electric fuel pump for a motor vehiclehaving an electronic controller for regulating the power of the fuelpump, said controller being arranged between a power supply and the fuelpump, and having a pressure sensor for monitoring a pressure which isgenerated by the fuel pump, characterized in that the electroniccontroller (3) is connected to a monitoring device (4) and means forconnecting the fuel pump (1, 2) to the power supply when the electroniccontroller (3) has a fault are provided.
 2. The device as claimed inclaim 1, characterized in that the electronic controller (3) or themonitoring device (4) has means for connecting the fuel pump (1, 2) tothe power supply when the pressure sensor (7) has a fault.
 3. The deviceas claimed in claim 1 or 2, characterized in that the connection of thefuel pump (1, 2) to the power supply is unregulated.
 4. The device asclaimed in at least one of the preceding claims, characterized in thatthe fuel pump (1, 2) has a switch (9, 10), in that the switch (9, 10)can be actuated by the monitoring device (4) and is designed to connectthe fuel pump (1, 2) to the electronic controller (3) in one position,and to the power supply in the other position.
 5. The device as claimedin at least one of the preceding claims, characterized in that theswitch (9, 10) has a relay (8).
 6. The device as claimed in at least oneof the preceding claims, characterized in that a single electroniccontroller (3) is designed to actuate a plurality of fuel pumps (1, 2).7. The device as claimed in at least one of the preceding claims,characterized in that the fuel pump (1, 2) is connected to a mechanicalpressure regulator (17).
 8. The device as claimed in at least one of thepreceding claims, characterized in that each of the fuel pumps (1, 2)has its own switch (9, 10).
 9. The device as claimed in at least one ofthe preceding claims, characterized in that the monitoring device (4)and the control unit (5) of the internal combustion engine have a commonconnection (15) for a diagnostic device.